Method for adjusting a phase angle of a phase modifier of a transmitting device

ABSTRACT

A method for adjusting a phase angle (φ) of a phase modifier ( 25 ) of a transmitting device which includes a quadrature modulator ( 3 ), a power amplifier ( 9 ), a quadrature demodulator ( 19 ) and differential amplifiers ( 26, 27 ). The power amplifier ( 9 ) is linearized via the feedback loop ( 16 ) according to the Cartesian feedback method. The phase modifier ( 25 ) supplies an oscillator signal to the quadrature demodulator ( 19 ), which signal is shifted by the phase angle (φ) to be adjusted with regard to the oscillator signal that is supplied to the quadrature modulator ( 3 ). An input signal with a constant inphase component (I) and a constant quadrature phase component (Q) is applied during each transmission burst in the instance of a closed feedback loop, and the quadrature component (VQM) and/or the inphase component (VIM) is measured at a measuring point ( 53, 61 ) located behind the output of the differential amplifiers ( 26, 27 ).

This application is a 371 of PCT/EP00/06078, filed Jun. 29, 2000, whichclaims priority to Germany application No. 199 46 669.6, filed Sep. 29,1999.

BACKGROUND OF THE INVENTION

The invention relates to a method for adjusting a phase angle of a phasemodifier of a transmitting device. The transmitting device comprises aquadrature modulator and a power amplifier which is linearized via aso-called Cartesian feedback loop with a quadrature demodulator.

EP 0 706 259 A1 discloses a transmitting device wherein a basic bandinput signal is supplied to a quadrature modulator via two differentialamplifiers. Said quadrature modulator performs quadrature modulation ofthe inphase component and the quadrature phase component of the complexinput signal. Power amplification takes place in a power amplifierconnected downstream the quadrature modulator. To compensate thenon-linerarity of this power amplifier a feedback loop is provided,generally designated as a Cartesian which separates the fedback signalinto a fedback inphase component and a fedback quadrature phasecomponent. The fedback inphase component is supplied, together with theinphase component of the input signal, to a first differentialamplifier, connected upstream the quadrature modulator. Correspondingly,the fedback quadrature phase component is supplied, together with thequadrature phase component of the input signal, to a second differentialamplifier. In this way the non-linearities of the power amplifier arecompensated via the fedback signal.

In a transmitting device operating according to the Cartesian feedbackmethod it is particularly important that the fedback signal is inputinphase. In order to achieve this, the signal of a local oscillator,which is required for the quadrature modulation and quadraturedemodulation, is supplied to the quadrature demodulator at a phase angleshifted with regard to the quadrature modulator. The phase shift takesplace in a phase modifier, the phase angle of which has to be adjusted.To adjust the phase angle, in EP 0 706 259 A1 a test mode is proposed,in which the feedback loop is interrupted at the output of thequadrature demodulator. A test signal is applied to the input of thequadrature modulator and the output signal of the quadrature demodulatoris measured. With a predetermined input signal the phase angle to be setcan be calculated from the real part and the imaginary part of theoutput signal of the quadrature demodulator.

Of disadvantage in the mode of operation proposed in EP 0 706 259 A1,however, is that the feedback loop for determining the phase angle hasto be opened each time. This method may be suitable for adjusting thephase angle once on taking into operation, but in the application of atransmitting device operating on the Cartesian feedback principle inaeronautical radio, in particular with digital aeronautical radiooperating according to the VDL standard (VHL digital link) in TDMASimplex mode, there is a necessity to check and possibly re-adjust thephase angle at each transmitting interval (transmitting burst). Thiscannot be done with the method emerging from EP 0 706 259 A1, owing tothe time-consuming separation of the feedback loop and the complicatedmeasurement process.

SUMMARY OF THE INVENTION

Therefore the object of the invention is to cite a method for adjustinga phase angle of a phase modifier of a transmitting device with a poweramplifier which is linearized according to the Cartesian feedbackprinciple, which enables correction or re-setting of the phase angle ateach transmitting interval.

The object is achieved by the characterising features of claim 1 inconjunction with the generic features.

The invention is based on the awareness that, by applying an inputsignal with a predetermined constant inphase component and apredetermined constant quadrature phase component, a deviation of thephase angle can be relatively easily determined. The feedback loop,consisting of quadrature modulator, power amplifier and quadraturedemodulator and the differential amplifiers, can therein remain closed.The method can be carried out at each transmitting interval, as it isnot time-consuming and does not require separation of the feedback loop.

Claims 2 to 9 relate to advantageous further developments of the methodaccording to the invention.

Applying an input signal with predetermined inphase component (I=const.)and without quadrature phase component (Q=0) and measuring thequadrature phase component can advantageously take place at the outputof the differential amplifier at the beginning of every transmittinginterval. During switching over from receive mode to transmit mode it isin any case advantageous to apply, in addition, for example, to threedata symbols, a reference signal with a pure inphase component withoutquadrature phase component at the beginning of the transmittinginterval. This reference signal can be used for determining the phaseaccording to the invention without taking extra time. With an inputsignal without quadrature phase component (Q=0) ideally no voltageoccurs at the output of the differential amplifier in the quadraturephase control loop. If a voltage is nevertheless measured at thismeasuring point this indicates a phase error, which can be corrected inthe next transmitting interruption interval or receiving interval.

The phase correction value can be immediately determined from themeasured quadrature phase component, optionally taking into account theadditionally measured inphase component, by an arcus tangens relation.The phase correction values assigned to the measured values can betabulated in a memory (look-up table) and read off immediately withoutfurther calculation. An alternative possibility for determining theoptimum phase correction value consists in a trial and error method, inwhich the phase angle is minimally altered experimentally during areceiving interval and in the subsequent transmitting interval, bymeasuring the quadrature phase component with the previously describedreference signal, it is ascertained whether the newly adjusted phaseangle yields a better result. If this is the case, the phase angle isfurther altered in this direction in the subsequent receiving interval.If the newly set phase angle yields a worsening, in the subsequentreceiving interval the phase angle is adjusted back to the previouslyset value. Due to this fine alignment, minimal phase fluctuations,resulting, for example, from a drift in temperature, can be re-correctedwhile operation is running.

Before the transmitting device is taken into operation for the firsttime it is advantageous to perform a preliminary adjustment of the phaseangle in such a way that a minimal output power results. For this casethe maximum self-damping of the system results, by contrast with thereverse case of maximum output power, resulting in maximum positivefeedback of the system. The signal of the feedback loop is in this casedamped.

A simplified embodiment example of the invention is described in greaterdetail below with reference to the drawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows a block diagram of an embodiment example of a transmittingdevice, suitable for the method according to the invention;

FIG. 2 shows a time-dependency diagram to explain the method accordingto the invention;

FIG. 3 shows a flow diagram to explain an embodiment example of themethod according to the invention and

FIG. 4 shows a diagram to explain the measuring of the phase correctionangle.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a transmitting device 1 suitable for carrying out themethod according to the invention in a basic block diagram.

A digital signal processor (DSP) 2 generates a complex input signal fora quadrature modulator 3, consisting of an inphase mixer 4, a quadraturephase mixer 5 and a summer 6, as well as a phase modifier 7. The complexinput signal consists of an inphase component I and a quadrature phasecomponent Q, wherein the inphase component I is supplied to the inphasemixer 4 and the quadrature phase component Q is supplied to thequadrature phase mixer 5. The output signal of a local oscillator 8 issupplied to the phase modifier 7, wherein the phase modifier 7 suppliesthis oscillator signal to the inphase mixer 4 without phase shift and tothe quadrature phase mixer 5 at a phase shift of 90°.

Connected downstream the quadrature modulator 3 is a power amplifier 9which supplies the quadrature-modulated signal, power-amplifiedcorresponding to the transmitting power of the transmitting device 1, toan antenna 13 via a circulator 10, a power detector 11 and atransmit-receive changeover switch 12. In the embodiment exampleillustrated in FIG. 1 the digital signal processor 2 acts simultaneouslyas control unit for the transmit-receive changeover and triggers thetransmit-receive changeover switch 12 in such a way that the antenna 13is connected to the power amplifier 9 in transmit mode and to a receiverdesignated as an RX in receive mode. The circulator 10, connected to theterminal resistance 14, serves to avoid feedback of possibly reflectedtransmitting power into the power amplifier 9.

In the signal path between the power amplifier 9 and the antenna 13 is adecoupler 15, which couples the output signal of the power amplifier 9into a feedback loop 16. In the feedback loop 16 is a changeover switch17, via which an input 18 of a quadrature demodulator 19 can beoptionally connected to the decoupler 15 or a terminal resistance 20.Between the decoupler 15 and the changeover switch 17 is a logarithmicpower detector 39. The quadrature demodulator 19 consists of a signaldivider 21, which divides the input signal equally between an inphasemixer 22 and a quadrature phase mixer 23. Further provided is a phasemodifier 24, to which the output signal of the local oscillator 8 issupplied via an adjustable phase modifier 25. Phase modifier 24 operateslike phase modifier 7 and supplies to the inphase mixer 22 anon-phase-shifted oscillator signal and to the quadrature phase mixer 23an oscillator signal phase-shifted by 90°, wherein the oscillator signalhas previously been phase-shifted in total by a phase angle φ by thephase modifier 25.

At the output of the inphase mixer 22 is a fedback inphase component I′and at the output of the quadrature phase mixer 23 is a fedbackquadrature phase component Q′. The inphase component I of the inputsignal is passed to the (+) input of a first differential amplifier 26,while the fedback inphase component I′ is passed to the (−) input of thefirst differential amplifier 26. Correspondingly the quadrature phasecomponent Q of the input signal is supplied to the (+) input of a seconddifferential amplifier 27, while the fedback quadrature phase componentQ′ is supplied to the (−) input of the second differential amplifier 27.By means of this feedback arrangement, generally designated as Cartesianfeedback, it is achieved that linearization errors of the poweramplifier 9 are compensated by the quadrature demodulator 19, arrangedin the feedback loop 16, and the differential amplifiers 26 and 27. Itshould therein be ensured, however, that the fedback signal I′, Q′ issupplied to the differential amplifiers 26 and 27 with a phase shift of0° with regard to the input signal I, Q. The correct phase position isset by the adjustable phase modifier 25, the phase angle φ of which canbe altered with the method according to the invention by the digitalsignal processor via a control signal.

As both the quadrature modulator 3 and the quadrature demodulator 19have a direct current offset (DC offset), this direct current offset hasto be correspondingly compensated. A third differential amplifier 28,arranged between the inphase mixer 22 of the quadrature demodulator 19and the first amplifier 26, serves this purpose. A fourth differentialamplifier 29 is arranged between the quadrature phase mixer 23 of thequadrature demodulator 19 and the second differential amplifier 27.While the fedback inphase component I′ is supplied to the (+) input ofthe third differential amplifier 28, a first compensation voltage V_(I1)is supplied to the (−) input of the third differential amplifier 28, sothe direct current offset in the I′ component of the quadraturedemodulator 19 is compensated at the output of the third differentialamplifier 28. Correspondingly the fedback quadrature phase component Q′is supplied to the fourth differential amplifier 29 at its (+) input,while a fourth compensation voltage V_(Q1) is supplied to its (−) input.

A fifth differential amplifier 30, to the (+) input of which the outputof the first differential amplifier 26 is supplied, while a thirdcompensation voltage V_(I2) is supplied to its (−) input, serves tocompensate the direct current offset of the quadrature modulator 3.Further provided is a sixth differential amplifier 31, the output ofwhich is connected to the quadrature phase mixer 5 of the quadraturemodulator 3 and to the (+) input of which the output of the seconddifferential amplifier 27 is supplied. A fourth compensation voltageV_(Q2) is supplied to the (−) input of the sixth differential amplifier31. The compensation voltages V_(I1), V_(Q1), V_(I2), and V_(Q2) aredrawn in as controllable voltage sources in FIG. 1 for betterillustration, however these compensation voltages are expedientlygenerated internally in the digital signal processor 2.

With fast changeover between transmit mode and receive mode there is aproblem, where a feedback loop 16 according to the Cartesian feedbackprinciple is used, that the high frequency signal path of the loop,consisting of the quadrature modulator 3, the power amplifier 9, thequadrature demodulator 19 and the differential amplifiers 26 and 27, hasto be interrupted during the changeover from transmit mode to receivemode, as the power amplifier 9 and the local oscillator 8 have to beswitched off. When the power amplifier 9 and the local oscillator 8 areswitched on again and the high frequency signal path is restored via thefeedback loop 16, a switching shock pulse is caused, as the voltages ofthe control system, in other words the output voltages of the twodifferential amplifiers 26, 27, run to the positive or negative controllimit stop when the high frequency signal path is open. This leads to anunacceptable sudden power variation to the maximum possible transmittingpower of the power amplifier 9. Therefore in FIG. 1, as well as the highfrequency signal path from the output of the differential amplifiers 26and 27 via the quadrature modulator 3, the power amplifier 9 and thequadrature demodulator 19 to the (−) input of the differentialamplifiers 26 and 27, two direct DC signal paths 32 and 33 are to beprovided which directly connect the output of the differential amplifier26 or 27, assigned in each case, to the (−) input of the respectivedifferential amplifier 26 or 27. The direct DC signal paths 32 and 33consist in the embodiment example illustrated in each case of acontrollable switch 34 or 35, which can be constructed, for example, asfield-effect transistors, and a resistance 36 or 37, connected inseries. During receive mode a constant OV potential can be maintained atthe input and output of the differential amplifier 26 and 27, so thechangeover to transmit mode takes place without shock pulses. Thefunction of the low impedance resistances 51 and 52, arranged parallelto the resistances 36 and 37 and able to be connected to the switches 34and 35 via a separate switch position, is explained in more detaillater.

FIG. 2 shows in a time-dependency diagram the sequence of the changeoverfrom receive mode to transmit mode. In the top partial diagram theoutput power TX is represented logarithmically as a function of thetime. Further illustrated in FIG. 2 and designated as RX is the signalof the latest possible receiving interval. In the partial diagram belowit the input signal I/Q is represented as a function of the time. Belowthis is the signal “S/E” for actuating the transmit/receive changeoverswitch 12 and the signal “DC loop” for actuating switches 34 and 35 ineach case as a function of the time t. The signal “BIAS” designates thesupply voltage for the power amplifier 9, while the signal “LO level”designates the level of the local oscillator 8.

As can be seen from FIG. 2, during the changeover from receive mode totransmit mode the procedure is as follows:

First the level of the local oscillator 8 is increased. Then the supplyvoltage (BIAS) for the power amplifier 9 is switched on and the switch17 subsequently actuated, so the input of the quadrature demodulator 19is switched over to the decoupler 15. After the high frequency feedbackloop has thus been closed, switches 34 and 35 are opened by the signal“DC loop” and the direct current paths 32 and 33 are thus interrupted.Finally, by means of the signal “S/E” the transmit/receive changeoverswitch 12 is switched over to transmit mode. Subsequently the inputsignal I/Q can be supplied to the quadrature modulator 3 via the (+)inputs of the differential amplifiers 26 and 27 and the output power TXthus successively increased (ramping).

In the time interval between times t₁ and t₂ an almost constant outputsignal is available. In the embodiment example an input signal I/Q isused as reference signal between times t₁ and t₂, consisting of aconstant inphase component (I=const.) without quadrature phase component(Q=0). This signal is applied as reference signal at the beginning ofevery transmitting interval before transfer of the actual data for aperiod of preferably three data symbols in the time interval betweentimes t₁ and t₂. Simultaneously at least the quadrature phase componentV_(QM) is measured at measuring point 53 in FIG. 1. Preferably theinphase component V_(IM) is also measured at measuring point 61. Since apure inphase component without quadrature phase component is used asinput signal, ideally, i.e. with correctly chosen phase angle φ for thephase modifier 25, the measuring signal V_(QM) at measuring point 53 iszero. If a deviating measuring voltage occurs this indicates a phaseerror which is to be corrected.

The method according to the invention for adjusting the phase angle φ isexplained using FIG. 3. The method is divided into pre-adjusting of thephase angle p, to be performed once when the transmitting device 1 istaken into operation (method steps 40), re-setting the phase angle φ ateach transmitting interval (transmitting burst) (method steps 41) andoptional fine re-setting of the phase angle φ at each transmittinginterval (method steps 42).

When the transmitting device 1 is taken into operation the phase angle φof the phase modifier 25 in the embodiment example illustrated in FIG. 3is pre-adjusted in such a way that the power P is measured as a functionof the phase angle φ by the logarithmic power detector 39 or by thepower detector 11. The phase angle φ is therein continually varied inthe range of 0° to 360°. Finally, the particular phase angle φ in whichthe measurement resulted in the minimum power P_(min) is set. Thismeasuring principle is based on the assumption that for the phase angleφ for which the minimum output power P_(min) results the feedback loop16 is optimally negatively fed back. The thus pre-adjusted phase angle φusually offers a good starting point for the adjustment method to bedescribed below, which is performed at each transmitting interval.During this measurement of the output power the signal of the feedbackloop 16 is damped, in order to avoid too great a positive feedback witha rough misadjustment of the phase angle φ, with the danger ofdestroying the power amplifier 9. In the embodiment example this dampingis achieved in that switches 34 and 35 are switched over to the lowimpedance resistances 51 and 52, in order to achieve strong negativefeedback of the differential amplifiers 26 and 27.

Alternatively series resistances, for example, could also be connectedin the feedback loop 16.

With the adjustment method according to the invention, as described, atthe beginning of every transmitting interval or transmitting burst areference signal with a pure inphase component (I=const.) withoutquadrature phase component (Q=0) is applied for a period of preferablythree data symbols and at least the quadrature phase component(measuring signal V_(QM)) is measured at the output of the seconddifferential amplifier 27 at measuring point 53. As the inphasecomponent I is constant, it is sufficient to relate the measuredquadrature phase component V_(QM) to the input inphase component I andto use them as an argument for the arcus tangens function, in order toobtain the phase correction value Δφ. Accuracy of measurement can beincreased in that the measured quadrature phase component V_(QM) isrelated not to the predetermined inphase component I at the input of thefirst differential amplifier 26, but to the inphase component V_(IM)measured at the output of the first differential amplifier 26. Thecorrected phase angle φ′ results from addition of the phase correctionangle Δφ to the previously adjusted phase angle φ. The phase correctionvalue Δφcan be read off in a stored table as a function of the measuredsignal V_(QM) or V_(QM) and V_(IM).

In the variant of the adjustment method described in FIG. 3 re-settingthe phase angle φ takes place by means of the arcus tangens functiononly until the obtained phase correction value Δφ is greater than apredetermined constant c. If the phase correction value Δφ is smallerthan the limit value c, a change is made to an iterative fine adjustmentmethod 42. This fine adjustment method 42 is based on a trial and errorprinciple. Before each transmitting burst the currently set phase angleφ is altered experimentally by a step width Δφ_(step) and then at thebeginning of the transmitting burst the measuring voltage V_(QM) ismeasured at measuring point 53, while at the input a pure inphasecomponent I without quadrature phase component applies. With a properlyadjusted phase angle φ the measuring voltage V_(QM) is ideally 0. If theamount |V_(QM)| of the measuring voltage V_(QM) is reduced by thevariation of the adjusted phase angle φ, this newly adjusted phase angleφ′ is better than the previously adjusted phase angle φ. The phase angleφ is optionally altered again in this direction for the nexttransmitting burst, in order to test whether the amount of the measuringvoltage V_(QM) therein decreases even further. The step width canoptionally be varied as a function of the amount of the measuringvoltage V_(QM). If the amount of the measuring voltage V_(QM) isgreater, however, the setting is put back to the previously set phaseangle φ.

This method is then repeated in the opposite direction with reversedalgebraic sign of Δφ_(step). If fine adjustment in the oppositedirection also does not result in an improvement, the previously setphase angle φ is the best value and is left for a predetermined period.After a period after which, for example, owing to a thermal drift, ashift in the phase angle φ may have resulted, the method described aboveis repeated.

FIG. 4 shows the predetermined constant input signal (I, Q), consistingof the inphase component I and the quadrature phase component Q, and themeasuring signal (V_(IM), V_(QM)) measured at the output of thedifferential amplifiers 26 and 27, consisting of the measured inphasecomponent VIM and the measured quadrature phase component V_(QM).

The predetermined desired phase angle φ_(soll) results therein from therelation $\varphi_{soll} = {\arctan\frac{Q}{I}}$

The measured actual phase angle φ_(ist) results from the relation$\varphi_{ist} = {\arctan{\frac{V_{QM}}{V_{IM}}.}}$

The phase correction value Δφ results from the relation${\Delta\varphi} = {{\varphi_{ist} - \varphi_{soll}}=={\arctan - \frac{V_{QM}}{V_{IM}} - {\arctan{\frac{Q}{I}.}}}}$

In the embodiment example described using FIG. 3 an input signal with apure inphase component has been used, wherein the input quadrature phasecomponent Q is zero, so φ_(sol1)=0. As the preceding relation shows,other input signals with other desired phase angles can also be used,however, wherein the use of the desired phase angle φ_(soll)=0 ispreferred owing to the resulting simplification of the measuringprocess.

The invention is not restricted to the embodiment example illustrated.In particular other algorithms than those illustrated in FIG. 3 can beused. The preliminary adjustment of the phase angle φ illustrated inFIG. 3 can also be done in other ways. Instead of an input signal with apure inphase component any chosen input signal with constant phase angleφ can be used.

1. A method for adjusting a phase angle of a phase modifier of atransmitting device, wherein said method comprises: providing thetransmitting device comprising: a quadrature modulator for quadraturemodulation of an inphase component and a quadrature phase component of acomplex input signal; a power amplifier, connected downstream of thequadrature modulator; a quadrature demodulator for quadraturedemodulation of an output signal of the power amplifier into a fedbackinphase component and a fedback quadrature phase component; a firstdifferential amplifier, connected upstream the quadrature modulator,said first differential amplifier having a first input supplied by theinphase component of the complex input signal and a second inputsupplied by the fedback inphase component; a second differentialamplifier, connected upstream the quadrature modulator, said seconddifferential amplifier having a first input of the second differentialamplifier supplied by the quadrature phase component of the complexinput signal and a second input of the second differential amplifiersupplied by the fedback quadrature phase component; and a phasemodifier, which supplies to the quadrature demodulator an oscillatorsignal, shifted with regard to an oscillator signal supplied to thequadrature modulator by the phase angle to be adjusted; applying aninput signal with a predetermined constant inphase component and apredetermined constant quadrature phase component at each transmittinginterval with a closed feedback loop containing the quadraturemodulator, the power amplifier, the quadrature demodulator, the firstdifferential amplifier and the second differential amplifier; measuringthe quadrature phase component and optionally the inphase component at afirst measuring point behind an output of the first differentialamplifier and a second measuring point behind an output of the seconddifferential amplifier; determining a phase correction value based onthe measured quadrature phase component and optionally the measuredinphase component; and correcting the currently set phase angle of thephase modifier by adding or subtracting the determined phase correctionvalue in a transmitting interruption interval, wherein the phase angleis not altered if the amount of the measured quadrature phase componentis smaller than a predetermined limit value.
 2. The method according toclaim 1, wherein the quadrature phase component of the complex inputsignal being applied has a value of zero, and the measuring at thesecond measuring point behind the output of the second differentialamplifier takes place at a beginning of every transmitting interval. 3.The method according to claim 1, wherein the phase correction value (Δφ)is determined by solving the following equation:Δφ=arc tan (V _(QM) /V _(IM))−arc tan (Q/I) wherein V_(QM) is themeasured quadrature phase component, V_(IM) is the measured inphasecomponent, Q is the predetermined quadrature phase component and I isthe predetermined inphase component.
 4. The method according to claim 3,wherein prior to or concurrent with activating the transmitting device,the phase angle of the phase modifier is preliminarily adjusted suchthat an output power is measured at a power detector connecteddownstream of the power amplifier and the phase angle is pre-adjustedsuch that a minimum of the output power results.
 5. The method accordingto claim 1, wherein the determining of the phase correction valuecomprises altering the phase angle by a step width in a first directionif the measured quadrature phase component is positive and altering thephase angle by a step width in an opposite direction if the measuredquadrature phase component is negative.
 6. The method according to claim5, wherein the step width depends on an amount of the measuredquadrature component.
 7. The method according to claim 1, wherein priorto or concurrent with activating the transmitting device, the phaseangle of the phase modifier is preliminarily adjusted such that anoutput power is measured at a power detector connected downstream of thepower amplifier and the phase angle is pre-adjusted such that a minimumof the output power results.
 8. A method for adjusting a phase angle ofa phase modifier of a transmitting device, wherein said methodcomprises: providing the transmitting device comprising: a quadraturemodulator for quadrature modulation of an inphase component and aquadrature phase component of a complex input signal; a power amplifier,connected downstream of the quadrature modulator; a quadraturedemodulator for quadrature demodulation of an output signal of the poweramplifier into a fedback inphase component and a fedback quadraturephase component; a first differential amplifier, connected upstream thequadrature modulator, said first differential amplifier having a firstinput supplied by the inphase component of the complex input signal anda second input supplied by the fedback inphase component; a seconddifferential amplifier, connected upstream the quadrature modulator,said second differential amplifier having a first input of the seconddifferential amplifier supplied by the quadrature phase component of thecomplex input signal and a second input of the second differentialamplifier supplied by the fedback quadrature phase component; and aphase modifier, which supplies to the quadrature demodulator anoscillator sigal, shifted with regard to an oscillator signal suppliedto the quadrature modulator by the phase angle to be adjusted; applyingan input signal with a predetermined constant inphase component and apredetermined constant quadrature phase component at each transmittinginterval with a closed feedback loop containing the quadraturemodulator, the power amplifier, the quadrature demodulator, the firstdifferential amplifier and the second differential amplifier; measuringthe quadrature phase component and optionally the inphase component at afirst measuring point behind an output of the first differentialamplifier and a second measuring point behind an output of the seconddifferential amplifier; determining a phase correction value based onthe measured quadrature phase component and optionally the measuredinphase component; and correcting the currently set phase angle of thephase modifier by adding or subtracting the determined phase correctionvalue in a transmitting interruption interval, wherein the quadraturephase component of the complex input signal being applied has a value ofzero, the measuring at the second measuring point behind the output ofthe second differential amplifier takes place at a beginning of everytransmitting interval and the determining of the phase correction valuecomprises altering the phase angle by a step width in a first directionif the measured quadrature phase component is positive and altering thephase angle by a step width in an opposite direction if the measuredquadrature phase component is negative.
 9. The method according to claim8, wherein the inphase component is measured at the first measuringpoint behind the output of the first differential amplifier.
 10. Themethod according to claim 9, wherein the phase correction value (Δφ) isdetermined by solving the following equation:Δφ=arc tan (V _(QM) /V _(IM))−arc tan (Q/I) wherein V_(QM) is themeasured quadrature phase component, V_(IM) is the measured inphasecomponent, Q is the predetermined quadrature phase component and I isthe predetermined inphase component.
 11. The method according to claim8, wherein the phase correction value (Δφ) is determined by solving thefollowing equation:Δφ=arc tan (V _(QM) /V _(IM))−arc tan (Q/I) wherein V_(QM) is themeasured quadrature phase component, V_(IM) is the measured inphasecomponent, Q is the predetermined quadrature phase component and I isthe predetermined inphase component.
 12. The method according to claim8, wherein the step width depends on an amount of the measuredquadrature component.
 13. The method according to claim 8, wherein thephase angle is not altered if the amount of the measured quadraturephase component is smaller than a predetermined limit value.
 14. Themethod according to claim 8, wherein prior to or concurrent withactivating the transmitting device, the phase angle of the phasemodifier is preliminarily adjusted such that an output power is measuredat a power detector connected downstream of the power amplifier and thephase angle is pre-adjusted such that a minimum of the output powerresults.
 15. A method for adjusting a phase angle of a phase modifier ofa transmitting device, wherein said method comprises: providing thetransmitting device comprising: a quadrature modulator for quadraturemodulation of an inphase component and a quadrature phase component of acomplex input signal; a power amplifier, connected downstream of thequadrature modulator; a quadrature demodulator for quadraturedemodulation of an output signal of the power amplifier into a fedbackinphase component and a fedback quadrature phase component; a firstdifferential amplifier, connected upstream the quadrature modulator,said first differential amplifier having a first input supplied by theinphase component of the complex input signal and a second inputsupplied by the fedback inphase component; a second differentialamplifier, connected upstream the quadrature modulator, said seconddifferential amplifier having a first input of the second differentialamplifier supplied by the quadrature phase component of the complexinput signal and a second input of the second differential amplifiersupplied by the fedback quadrature phase component; and a phasemodifier, which supplies to the quadrature demodulator an oscillatorsignal, shifted with regard to an oscillator signal supplied to thequadrature modulator by the phase angle to be adjusted; applying aninput signal with a predetermined constant inphase component and apredetermined constant quadrature phase component at each transmittinginterval with a closed feedback loop containing the quadraturemodulator, the power amplifier, the quadrature demodulator, the firstdifferential amplifier and the second differential amplifier; measuringthe quadrature phase component and optionally the inphase component at afirst measuring point behind an output of the first differentialamplifier and a second measuring point behind an output of the seconddifferential amplifier; determining a phase correction value based onthe measured quadrature phase component and optionally the measuredinphase component; and correcting the currently set phase angle of thephase modifier by adding or subtracting the determined phase correctionvalue in a transmitting interruption interval, wherein prior to orconcurrent with activating the transmitting device, the phase angle ofthe phase modifier is preliminarily adjusted such that an output poweris measured at a power detector connected downstream of the poweramplifier and the phase angle is pre-adjusted such that a minimum of theoutput power results.
 16. The method according to claim 15, wherein thephase angle is not altered if the amount of the measured quadraturephase component is smaller than a predetermined limit value.
 17. Themethod according to claim 15, wherein the signal of the feedback loop isdamped during measurement of the output power.
 18. The method accordingto claim 15, wherein the inphase component is measured at the firstmeasuring point behind the output of the first differential amplifier.19. The method according to claim 18, wherein the phase angle is notaltered if the amount of the measured quadrature phase component issmaller than a predetermined limit value.
 20. The method according toclaim 15, wherein the determining of the phase correction valuecomprises altering the phrase angle by a step width in a first directionif the measured quadrature phase component is positive and altering thephase angle by a step width in an opposite direction if the measuredquadrature inphase component is negative.